Durability of Adhesive-Bonded Aluminum Joints Exposed to Outdoor Weathering

The effects of outdoor weathering on the strength of aluminum adhesive-bonded joints exposed for periods up to 4½ years have been determined. Three commercial epoxy resin adhesives were included in the evaluation. The results showed that improvements are needed in both adhesive formulation and surface pretreatment of aluminum to give joints which will withstand weathering for periods in excess of five years. Failure of bonds invariably occurred at or near the adhesive-adherend interface, thus showing the importance of metal surface properties on the durability of adhesive bonds. Results of both outdoor exposure and accelerated weathering tests emphasized that initial bond strength measurement is of no use in predicting the durability or service performance of a given adhesive.